The Scotland international had an operation 11 weeks ago and missed the play-offs after sustaining the injury against Burnley in April.
He will now begin work on the treadmill in his bid to be ready for first-team action in the autumn.
Blades' physio Paul Teather said: "We're pleased with how things are going and happy that Gary is continuing to work hard.
"He's on track to achieving his goal and, despite this tedious and slow process, at least he can see a carrot dangling in front of him now."
Naysmith's progress is a timely boost for manager Kevin Blackwell, who is resigned to losing both young defenders Kyle Naughton and Kyle Walker to either Everton or Tottenham this summer.